Barbs are fin nippers, that should be in thier description, most barbs that is, not ALL. A lot of fish could be described as fin nippers if not kept properly, Zebra/leopard danios could be classed as fin nippers if kept in small schools, <6.
Puffers are the ultimate fin nipper. Collumesus Asselus (south american puffer, Brazillian puffer) is a prime example. My preffered lfs has a lable on them that says 'not to be kept with long fined fish' this is BS, they are species only fish, to be kept on thier own. When small they will keep to theselves, but as they grow they will take on fish four times thier size.
Angels need an 18" high tank, at least. A 48" L x 18" H x 12" W would be preferred, 36" L is doable, but not ideal.
Jon